title: Genetic variation in the vitamin D receptor, plasma 25-hydroxyvitamin D, and biomarkers of cardiometabolic disease in Caucasian young adults.
abstract: OBJECTIVE
  Vitamin D regulates gene transcription by binding to the vitamin D receptor (VDR), potentially affecting cardiometabolic disease risk. However, studies of 25-hydroxyvitamin D [25(OH)D] and cardiometabolic disease are inconsistent. Inconsistencies may result from unaccounted for interactions between VDR genetic variants and 25(OH)D. We examined the effect of 25(OH)D on the association between VDR variants and cardiometabolic disease biomarkers.
  
  
  METHODS
  The relationship between 25(OH)D, 24 VDR variants, and 10 cardiometabolic biomarkers was examined in 488 Caucasians aged 20-29 years. Covariate-adjusted general linear models were used to examine the interaction effect of 25(OH)D × VDR on each biomarker. When interactions were significant (p < 0.05), relationships were further examined with analysis of covariance, stratified by tertiles of 25(OH)D and adjusted for multiple comparisons.
  
  
  RESULTS
  In the lowest tertile of 25(OH)D, major allele homozygotes for rs3819545 had higher insulin and HOMA-IR than minor allele carriers (p ≤ 0.002). Fasting insulin and HOMA-IR were lower in the highest than the lowest tertile of 25(OH)D among major allele homozygotes (p < 0.0001), but minor allele carriers had similar levels regardless of vitamin D status.
  
  
  CONCLUSIONS
  We identified 25(OH)D-dependent associations between rs3819545 and glycemic dysregulation biomarkers. Major allele homozygotes with low vitamin D status may be at increased risk of insulin resistance.
authors.affiliation: Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, Ont., Canada.
authors.forename: Bibiana
authors.initials: B
authors.lastname: García-Bailo
authors.forename: Joseph
authors.initials: J
authors.lastname: Jamnik
authors.forename: Laura A
authors.initials: LA
authors.lastname: Da Costa
authors.forename: Alaa
authors.initials: A
authors.lastname: Badawi
authors.forename: Ahmed
authors.initials: A
authors.lastname: El-Sohemy
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood*; D002318:Cardiovascular Diseases / Q000097:blood* / Q000208:ethnology / Q000235:genetics; D005260:Female; D014644:Genetic Variation; D055106:Genome-Wide Association Study; D006801:Humans; D007333:Insulin Resistance / Q000208:ethnology / Q000235:genetics; D008297:Male; D008659:Metabolic Diseases / Q000097:blood* / Q000208:ethnology / Q000235:genetics; D020641:Polymorphism, Single Nucleotide; D018167:Receptors, Calcitriol / Q000235:genetics*; D012307:Risk Factors; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D044465:White People / Q000235:genetics; D055815:Young Adult
chemical_list: D015415:Biomarkers; D018167:Receptors, Calcitriol; D014807:Vitamin D; C104450:25-hydroxyvitamin D